AWStats is a log analyzer that gives you nice summaries about
who's accessing your web server, when they're accessing it, how much
bandwidth they're using, etc. Here's a quick run through installing
and using AWStats on Gentoo.

Install AWStats:

# emerge -av awstats

Optionally, copy the log files from a remote server:

$ rsync -avz example.net:/var/log/apache2/ example-logs/

Configure AWStats by adjusting the model configuration distributed
with AWStats.

Because awstats.pl can be invoked interactively through your browser
(depending on how you have it installed), it has a fairly restricted
path. In order to run awstats on files in a random directory
(e.g. for processing your server's logs on another host) you should
use the -configdir option. Here's an example of parsing the all the
archived logs (my logs are archived as access_log-YYYYMMDD.gz):